South Africa 19.1.2016 10:07 am

Satellite tech finds sinkhole

LIFE-THREATENING POINTERS. Water spurts out of a subterranean
depression detected by satellite images. Picture: Supplied

LIFE-THREATENING POINTERS. Water spurts out of a subterranean depression detected by satellite images. Picture: Supplied

New imaging technology needs more tests, but SA has a viable detection system of earth cracks.

Scientists at the Council for Scientific and Industrial Research (CSIR) using state-of-the-art satellite imaging technology they have developed, detected the formation of a sinkhole in Centurion.

While sinkholes happen without warning, the appearance of tension cracks and surface subsidence are often early warning signs. The technology can be used to detect the deformations before they turn into sinkholes.

“A lot of additional work will need to be performed to test the operational limitations of the technique,” said Dr Jeanine Engelbrecht, CSIR’s senior re – searcher in synthetic aperture radar.

“However, the results prove that a sinkhole early-warning system may be on the cards in the near future.” The sinkhole was discovered when scientists processed historical satellite imagery over the greater Tshwane area and also started with new image acquisitions that will be an ongoing endeavour.

“Our analysis indicated that surface subsidence was taking place at an unpopulated site in Centurion,” said Engelbrecht. “The subsidence was detected with a total of 6.6cm of deformation recorded between June and August last year. The deformation features was about 100m in diameter.”

In December, scientists visited the property where the subsidence was taking place and found a sinkhole had indeed been formed. “The water supply pipe was leaking and, initially, the sinkhole was about 0.5 x 1 m in extent,” said Engelbrecht. “However, later on the same morning, the pipe burst spectacularly, resulting in a continuous jet of water spraying from the ground.

“We also observed tension cracks of tens of metres long surrounding the deformation feature,” she said. Engelbrecht said the pipe may have been leaking for some time, resulting in a cavity in the dolomite. This process would have caused the deformation features that were detected on the satellite imagery.

According to CSIR, vast areas in South Africa are under – laid by dolomitic rock, which is known to be associated with sudden, catastrophic collapse, also known as sinkholes.

“Over 3 000 sinkhole and subsidence events have been recorded in South Africa be – tween the early ’60s and the end of 2012,” said the CSIR in a statement. “The consequences of sinkhole formation are severe and have resulted in the deaths of at least 39 people over the past 50 years in South Africa.”




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